This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This is an NIMH-funded and IRB approved protocol. 288 subjects between the ages of 7 and 25 will be recruited from Dr. Vaidya's patient lists and by flyers. Half of the participants (72 female and 72 male) will have attention deficit hyperactivity disorder (ADHD) treated with stimulant drugs for at least 1 year. Their diagnosis will be confirmed by DSM-IV criteria, BCSC and ADHD Rating Scales. The healthy, non-ADHD control group will have 72 female and 72 male participants who will be age and IQ matched. Participants will be excluded if they have internalizing or externalizing scores on the Childhood Behavior Checklist, or if they have any history of prior psychological therapy or psychoactive drug treatment. 100 subjects per year will be studied in YEARs 1 and 2, and 88 in YEAR 3.